With the increasing use of computers and electronic communication equipment, documents are increasingly being stored, transmitted and displayed in electronic form. In many instances, it is desired to convert the original hardcopy of a document into electronic or digital form in order to store, transmit and/or display the document more efficiently. However, once an original document has been converted to digital form, it is often necessary to edit or annotate the digital version of the document. For example, it may be desired to electronically transmit the digital form of a document by telephone or computer network to a remote location where the document is displayed on a computer screen or the like, and then incorporate handwritten notations on the displayed document. As another example, where the original version of a document is to be stored in digital form for archival purposes, it may also be desired to digitally store any handwritten markings made on the original document. As a further example, it may be desired to create a drawing or other document by hand, while at the same time creating and storing a digital version of the document.
One area of increasing interest is teleconferencing systems, which allow multiple groups in remote locations to communicate with each other. The simplest teleconferencing systems use speaker telephones patched together in a conference call, while more elaborate systems use specially equipped rooms with full motion video, high fidelity sound and very high capacity communication links to produce broadcast quality sound and video interconnections among groups in two or more locations. The objective of these systems is to provide a level of communication among remote individuals or groups of people which approaches the level achieved in face-to-face meetings. An essential part of many meetings is the ability to share documents and to interact with the documents in some manner. For example, participants in a face-to-face meeting may underline or circle parts of a document for emphasis, or make corrections or annotations in the margin. In the case of a technical drawing, the participants may sketch in changes or additions. During a teleconference, there is a need for the participants to edit documents in such a manner that allows persons at each remote location to see the annotations.
Another area of increasing interest is in the medical field, where X-rays and other graphical images are increasingly being stored in digital form to simplify handling and archiving. However, doctors often prefer to work with the original X-ray rather than with a displayed digital image. It is very common for a doctor to make notes and marks on an X-ray in order to record or explain the doctor's analysis. A need exists to store the doctor's notes and markings in digital form along with the document upon which the markings are made.
Various digitizers are known in the prior art for converting the x-y position of a stylus into digital form. In these digitizers, a stylus simulating a writing instrument is drawn or selectively positioned on the digitizer surface. The device responds to the position of the stylus to generate digitized signals that are typically conveyed to a host computer. Such x-y digitizers are usually activated by electromagnetic coupling between the stylus and the work surface, but can also be activated by electrostatic coupling, touch, optical, and ultrasonic means.
Conventional electromagnetic x-y digitizers are disclosed in U.S. Pat. Nos. 3,851,097, 4,552,991, 4,570,033, 4,600,807, 4,633,436, 4,727,588, 4,841,290, 5,153,386, 5,155,813 and 5,272,470.
Touch controlled x-y digitizers are disclosed in U.S. Pat. Nos. 4,455,452 and 5,274,362.
Optical x-y digitizers are disclosed in U.S. Pat. Nos. 4,688,933, 5,051,736, 5,073,770, 5,159,322 and 5,164,585.
An ultrasonic x-y digitizer tablet is disclosed in U.S. Pat. No. 4,845,684.
Several conventional x-y digitizers have been used in conjunction with computer display screens, wherein the digitizer is mounted on or behind the screen. When the digitizer is mounted on the display screen, it is provided in the form of a transparent sheet. Such overlapping digitizers and display screens are disclosed in U.S. Pat. Nos. 4,723,836, 4,827,410, 4,873,398 and Re 34,476.
The use of a transparent x-y digitizer mounted on a computer screen to edit an electronic version of a document displayed on the screen is known in the prior art, as disclosed in U.S. Pat. Nos. 5,027,198 and 5,239,373. In these systems, editing is performed directly on the computer screen rather than on the hardcopy of a document.
The above-noted U.S. patents are incorporated by reference herein.
The present invention has been developed in view of the foregoing, and to overcome other deficiencies of the prior art.